## Audio visual topic limiting reactant assessment

Tara 1F
Posts: 21
Joined: Fri Jun 23, 2017 11:39 am

### Audio visual topic limiting reactant assessment

Question: How many moles of CO2 (g) are produced when 1kg of CaCO3 (s) is used to neutralise an acid spill? The equation for the reaction at 1atm and 25 degrees celsius is CaCO3 (s) + H2SO4 (aq) --> CaSO4 (s) + CO2(g) + H20 (l) Can someone explain how to do this question, the right answer is 10 moles but I am not getting that answer. Thanks!

Sarah_Wilen
Posts: 62
Joined: Fri Jun 23, 2017 11:39 am
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### Re: Audio visual topic limiting reactant assessment

Friend, 'tis I.

Let us walkthrough some potential blunders whilst solving this problem:
1) Is it balanced? I think yes
2) Did you convert CaCO3 into kg?

Now I shall walkthrough some steps:
1) Balanced ok yay
2) Convert 1.00 kg of CaCO3 into grams (1.00 kg=1000 g)
3) Convert CaCO3 into moles by using its molar mass (100.1 g CaCO3)
4) If I had one mole of CaCO3, I would produce one mole of CO2 as shown by the stoichiometric coefficient of 1 in front of CO2.
5) I solve all that fun and find that 10 moles of CO2 would be made.
6) Yay
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Kyle Sheu 1C
Posts: 87
Joined: Fri Jun 23, 2017 11:39 am

### Re: Audio visual topic limiting reactant assessment

This is a question which tests your knowledge of limiting reactants and dimensional analysis (aka unit conversion). The given chemical reaction is balanced and has a 1:1 ratio for all reactants:products, meaning that for ever 1 mole of each reactant that's consumed, 1 mole of each product will be formed.

We now need to convert 1kg calcium carbonate (CaCO3) into moles. Thus:

1kg CaCO3 * (1000g CaCO3/1kg CaCO3) * (1mol CaCO3/100.09g CaCO3)=9.991 mol CaCO3

By converting kg to g, and g to moles using molar mass, we determine the moles of CaCO3 used to neutralize the acid. Since there's a 1:1 ratio, this means that 9.991 mol CO2 will be produced. Rounding to one significant figures leaves us with 10 moles.

Picture of work is attached below (apologies for the low definition)

Please let me know if there's anything I can clear up!
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Last edited by Kyle Sheu 1C on Thu Jun 29, 2017 6:11 pm, edited 1 time in total.

Chem_Mod
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### Re: Audio visual topic limiting reactant assessment

Great discussion!